Thesis (doctoral)--Würzburg, 1954. / Includes bibliographical references (p. I-V).

Thesis (Ph. D.)--Columbia University, 1933. / Vita. Bibliography: p. 23.

Thesis (Ph. D.)--University of Wisconsin--Madison, 1952. / Typescript. Vita. eContent provider-neutral record in process. Description based on print version record. Includes bibliographical references (leaves 43-48).

Thesis (Ph. D.)--Princeton University, 1924.

Thesis (Ph. D.)--Columbia University, 1937. / Vita. Bibliography: p. 47-49.

The possibility of evaluating the quality of blueberry fruit in chemical terms rather than by color or organoleptic methods was considered. The fruit of three varieties of commercial highbush blueberries at four stages of physiological maturity was analysed for total solids, water-insoluble solids, soluble solids, titratable acids, total acids, volatile acids, reducing sugars, total sugars and sugar-acid ratios. Differences among varieties and stages of physiological maturity were sought by use of the above measurements supplemented by a study of the individual organic acid patterns of the fruit. Meaningful differences were evident among the four stages of physiological maturity for all measurements except volatile acids and total solids. Varietal differences were evident from measurements of the pH, soluble solids, sugar-acid ratios, and a number of the individual organic acids. / Land and Food Systems, Faculty of / Graduate

Based on the initial exploratory results of single-phase (acidogenesis and methanogenesis takes place in one vessel) whey biomethanation studies, a two-phase (acidogenesis and methanogenesis takes place in two separated serial vessels) biomethanation process was found to be more suitable for dealing with the current whey utilisation and/or disposal problem. Acidogenesis was found to be less understood in comparison to methanogenesis and therefore acidogenesis became the central problem of this thesis. Given that 90% of the five-day biochemical oxygen demand in whey is due to lactose, continuous culture (Chemostat) experiments were undertaken to examine the general mechanism of lactose acidogenesis by a mixed undefined culture using ¹⁴C-labeled tracers. Also the influence of whey protein (mainly β-lactoglobulin) on the general fermentation scheme was addressed. Experimental factors included a pH range of 4.0 to 6.5, a mesophilic temperature of 35°C and a dilution rate (D) range of 0.05 to 0.65 h⁻¹. At a fixed pH level, the observed variability in the main acidogenic end products (acetate, propionate, butyrate and lactate) with respect to D were found to be a consequence of the systematic separation of the various microbial groups involved in acidogenesis. Batch incubation of a [¹⁴C(U)]-lactate tracer with chemostat effluent samples and preparative separation of the end products followed by a liquid scintillation assay of the location of the radio activity demonstrated that a microbial population lactate to other end products and hence the observed increase in lactate concentrations at high D values. Further use of [¹⁴C(U)]-butyrate and [¹⁴C(2)]-propionate revealed the predominant carbon flow routes from pyruvate to the various end products. A qualitative lactose acidogenic fermentation model was proposed, in which lactose is converted to pyruvate via the Embden-Meyerhof-Parnas pathway. Pyruvate in a parallel reaction is then converted to lactate and butyrate. In the presence of hydrogen reducing methanogens lactate is converted to acetate in a very fast reaction and not propionate as previously believed-. The implications of these findings with regard to optimising the acidogenic phase reactor are discussed. Acidogenic fermentation of protein together with lactose did not affect the carbon flow scheme. In the D range of 0.05 to 0.15 h⁻¹ low pH (pH < 5.0) was found to favour the butyrate route at the expense of the lactate route and at high pH (pH > 5.5) the lactate route was favoured at the expense of the butyrate route, the pH region of 5.0 to 5.5 being the transition range. In order to describe the microbial growth, the Monod chemostat model was chosen among the various alternatives, because of its simplicity and its physico-chemical basis. The estimated model parameters are reported. / Applied Science, Faculty of / Chemical and Biological Engineering, Department of / Graduate

The present work is a part of a systematic investigation of the frequency shifts in infrared absorption produced by changing to the anions carbonyl containing acidic compounds.

The physicochemical characteristics of seven cold-pressed flaxseed oils sold in New Zealand were investigated for their fatty acid composition, tocopherol composition, moisture and volatile matter, free fatty acids, chlorophyll pigments, unsaponifiable matter, total phenolic acids and flavanoids, and colour. The seven cold-pressed flaxseed oils exhibited significant variations in their physicochemical characteristics. Quality of the oils in terms of oxidative stability was also investigated. Four oils were found to be within the limit of good stability oil indices, measured in terms of peroxide value, p-anisidine value, conjugated dienoic acids, specific extinction in ultraviolet spectrum, acid value and food oil sensor readings (to indicate total polar compounds). The role of minor constituents in the oxidative stability of two selected oils with different levels of fatty acid composition and minor constituents was investigated. Pan heating at 150�C caused loss of tocopherols, plastochromanol-8, phenolic acids, chlorophyll pigments, β-carotene and lutein and changes in the fatty acid composition. The pan-heated oils exceeded the limit of good stability oil indices using the measurement mentioned above except for acid value. The addition of α-tocopherol to the oils did not provide enhanced protection to the oils in accelerated aging of oil tests at 60�C. It was most likely that phenolic acids present in the oils played a dominant role in the oxidative stability of the oils. Lipase-catalyzed transesterification of triolein with cinnamic and ferulic acids using a commercially available immobilized lipase B from Candida antarctica (Novozym 435) was conducted to evaluate the antioxidant activity of the lipophilized products as model systems for enhanced protection of unsaturated oil. The lipophilized products were identified using Electrospray Ionization-Mass Spectroscopy (ESI-MS). Separation and isolation of two classes of lipophilized products was also achieved using a solid phase extraction method developed in this study for further investigation into the structure-free radical scavenging activity. Free radical scavenging activity was determined using the 2,2-diphenyl-1-picrylhydrazyl radical (DPPH) method. The polarity of the solvents proved important in determining the free radical scavenging activity of the substrates. Ferulic acid showed much higher free radical scavenging activity than cinnamic acid, which had limited activity. The esterification of cinnamic acid and ferulic acid with triolein resulted in significant increase and decrease in the free radical scavenging activity, respectively. These opposite effects were due to the effect of addition of electron-donating alkyl groups on the predominant mechanism of reaction (hydrogen atom transfer or electron transfer) of a species with DPPH. The effect of esterification of cinnamic acid was confirmed using ethyl cinnamate which greatly enhances the free radical scavenging activity. Although, compared with the lipophilized cinnamic acid product, the activity was lower. The free radical scavenging activity of the main component isolated from lipophilized cinnamic acid product using solid phase extraction, monocinnamoyldioleoylglycerol, was as good as the unseparated mixture of lipophilized product. Based on the ratio of a substrate to DPPH concentration, lipophilized ferulic acid was a much more efficient free radical scavenger than lipophilized cinnamic acid. Lipase-catalyzed transesterification of flaxseed oil with cinnamic and ferulic acids using Novozym 435 was conducted to evaluate whether the lipophilized products provided enhanced antioxidant activity in the oil. The lipophilized products were identified using ESI-MS and were examined for their free radical scavenging activity toward DPPH in ethanol and ethyl acetate. Ferulic acid showed the highest free radical scavenging activity among all substrates tested while cinnamic acid had negligible activity. The effect of esterification of cinnamic acid and ferulic acid with flaxseed oil was similar to that with triolein. Lipophilized ferulic acid was a better free radical scavenger as compared with lipophilized cinnamic acid and extended the naturally-occuring antioxidant capacity of the flaxseed oil. Lipophilized cinnamic acid did not provide much enhanced radical scavenging activity in the flaxseed oil as the presence of natural hydrophilic antioxidants in the oil had much greater radical scavenging activity. It may still be useful for unsaturated oils with a small amount of natural antioxidants in them. Lipophilized cinnamic and ferulic acids showed higher free radical scavenging activity when tested in a less polar solvent (ethyl acetate) whereas ferulic acid showed better activity in a more polar solvent (ethanol). These results indicate that the choice of solvent for the DPPH assay is critical in evaluating the free radical scavenging activity of substrates of differing polarity, and support previous observations by other authors that the solubility of an antioxidant in relation to the site of oxidation is an important factor for consideration in the use of antioxidants.

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